PC133 RAM on PC100 Bus

[jjsimas]

I bought some Crucial PC133 7.5 ns, but I am only going to run it at PC100.

I want to know if I run it at PC100, will it run at 8 ns.

If the nanoseconds is tied to the bus speed, then by cross multiplication I find that at a 100 mhz bus speed, it will run at 9.4 ns.

Information please.

Jason

 

[andylawcc]

lets gets some technical term straight,
PCXXX describe the MEMORY's Speed,
for the BUS speed, its called FSB,
both with Units of mhz.

10 ns = 100mhz
8 ns = 125mhz (coz 1000/8)
7.5 ns = 133mhz (1000/7.5)

however, many PC100 use 8ns chips, while 70 percent of PC133 has 7.5 while the others are mostly 7ns


so if your Memory is PC133, (hence 133 mhz)
and your bus speed is 100mhz, the Memory will also be the same 100mhz (so 10 -ns actually)
some motherboard may allow you abjust the memory to run it Asynchrously (different speed from the FSB) but its fixed +/- 33mhz.

 

[HD2GO]

I don't know where you got the 8ns and 9.4ns. If you put PC133 SDRAM in your PC100 system, you will be running your PC133 at 100MHz; unless you overclock your memory bus. This means you will run your memory clock at a period of 10ns; kind of an overkill to use PC133 memory in this system unless you bought the PC133 for future proving purpose.

 

[jjsimas]

andylawcc:

Oh yes, that vocabulary lesson really was relevant to my post -- not.

By the way, PCXXX is not a speed, nor does it have units of mhz.

PCXXX is a standard.

Jason

 

[fast_eddie]

BTW, you will not 'hurt' the PC133 by running it at 100MHz. I have even mixed PC100 & PC133 on 100FSB with no ill effects.

 

[Regalk]

PC133 is backwards compatible. So the answer is a simple yes.